feat(i18n): add Turkish (tr) locale support

Add a complete Turkish locale to the WebUI and login page so users can
select Türkçe in Settings, with speech recognition via tr-TR.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/test_pr1721_rtl_salvage.py

@@ -112,5 +112,5 @@ def test_rtl_in_config_defaults_and_writable_keys():
 def test_rtl_localized_in_all_locales():
     js = I18N.read_text(encoding="utf-8")
     # Count occurrences — should match the 11 locale blocks
-    assert js.count("settings_label_rtl:") == 11
-    assert js.count("settings_desc_rtl:") == 11
+    assert js.count("settings_label_rtl:") == 12
+    assert js.count("settings_desc_rtl:") == 12